title: Four-compartment model and validation of deuterium dilution technique to estimate fat-free mass in Mexican youth.
abstract: OBJECTIVE
  To validate the measurement of fat-free mass (FFM) with the deuterium oxide (D(2)O) dilution technique (2C) against the four-compartment (4C) model in Mexican children.
  
  
  METHODS
  This was designed as a cross-sectional, non-probabilistic study. Sixty subjects (30 male and 30 female) 6-14 y of age were recruited and completed the study during 5 mo. Total body water was measured using the D(2)O dilution technique and FFM was calculated using Fomon's (6-10 y) and Lohman's (11-14 y) hydration constants. Body composition using the 4C model was calculated with Lohman's equation.
  
  
  RESULTS
  Group mean accuracy showed no differences in FFM determined by D(2)O dilution and the 4C model (1.24 kg, P > 0.4), by gender (2.1 kg, P > 0.2), or by method-by-gender interaction (P > 0.7). FFMs were 26.9 and 25.7 kg by the 4C and 2C models, respectively. The test for coincidence of slopes and intercepts between the 2C and 4C models and the line of identity were not different (P > 0.05). Precision by R(2) explained 98% of the variance (standard error of the estimate 1.2 kg). Bias for the difference in FFM was not significant (-1.27, 95% confidence interval -1.5 to -0.9) and no association between the mean of the differences and the magnitude of the measurements was found (P > 0.05). Mean bias was -1.27 kg for FFM (P > 0.05), and limits of agreement were -3.1 to 0.8 kg.
  
  
  CONCLUSIONS
  The D(2)O dilution technique used with these hydration constants was accurate, precise, and free of bias in Mexican children and adolescents compared with the 4C model.
authors.affiliation: División de Nutrición, Centro de Investigación en Alimentación y Desarrollo, AC, Hermosillo, Sonora, Mexico.
authors.forename: Erik
authors.initials: E
authors.lastname: Ramírez
authors.forename: Mauro E
authors.initials: ME
authors.lastname: Valencia
authors.forename: Silvia Y
authors.initials: SY
authors.lastname: Moya-Camarena
authors.forename: Heliodoro
authors.initials: H
authors.lastname: Alemán-Mateo
authors.forename: Rosa O
authors.initials: RO
authors.lastname: Méndez
mesh_terms: D000293:Adolescent; D001823:Body Composition / Q000502:physiology*; D001834:Body Water / Q000378:metabolism* / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D015519:Bone Density / Q000502:physiology; D002648:Child; D003430:Cross-Sectional Studies; D017666:Deuterium Oxide; D005260:Female; D006801:Humans; D007201:Indicator Dilution Techniques / Q000592:standards*; D008297:Male; D008433:Mathematics; D008800:Mexico; D018482:Muscle, Skeletal / Q000378:metabolism*; D009765:Obesity / Q000175:diagnosis / Q000453:epidemiology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012737:Sex Factors
chemical_list: D017666:Deuterium Oxide